[SOLVED] KDE doesn't boot

[cfgauss]

I have SDDM configured to automatically login my user. X boots and there's a cursor arrow on a black background but KDE never boots. As a workaround, I switch to another VT and kill X, which brings me to the SDDM login window. From there providing my password boots X and then KDE normally.

Any debugging hints will be gratefully received.

[SOLVED] Thanks to pickd.mask for suggesting that the new pam-1.4.0-r1 might be the culprit. Downgrading to 1.3.1-r2, which automatically downgraded pambase to 20200304, restored a successful KDE boot. [/SOLVED]

[pickd.mask]

Could be recent pam and pambase upgrade. At least it broke login for me with 1.4.0 update.
Try to downgrade pam from 1.4.0 to 1.3.1-something and downgrade pambase accordingly.